Resin compositions, carbon material dispersion compositions, composite slurry, electrode films, secondary batteries, and vehicles

Abstract

The present invention provides a resin composition and a carbon material dispersion composition that can achieve both good dispersibility and good electrode characteristics. Furthermore, it provides a composite slurry that can produce an electrode film with high conductivity and adhesion, and more specifically, a secondary battery having excellent rate characteristics and cycle characteristics, and a vehicle that is safer and has improved fuel efficiency by having the secondary battery. [Solution] A resin composition is provided comprising a copolymer (X) having alkylene structural units and nitrile group-containing structural units, and an alkali metal, wherein the alkali metal content is 50 ppm or more and less than 10,000 ppm, and the resistivity when the resin composition has a non-volatile content of 8% by mass due to N-methyl-2-pyrrolidone is 5,000 Ω·cm or more and 25,000 Ω·cm or less.

Description

[Technical Field]

[0001] This disclosure relates to resin compositions and carbon material dispersion compositions. More specifically, it relates to carbon material dispersion compositions comprising a resin composition and a carbon material, composite slurry comprising a carbon material dispersion composition and an active material, electrode films coated therewith, a secondary battery comprising an electrode having an electrode film and an electrolyte, and a vehicle equipped with a secondary battery. [Background technology]

[0002] With the spread of electric vehicles and the miniaturization, weight reduction, and increased performance of portable devices, there is a growing demand for secondary batteries with high energy density and higher capacity. Against this backdrop, non-aqueous electrolyte secondary batteries, particularly lithium-ion secondary batteries, which utilize non-aqueous electrolytes due to their high energy density and high voltage characteristics, are increasingly being used in many devices.

[0003] The negative electrode materials used in these lithium-ion secondary batteries are carbon materials, such as graphite, which have a low potential close to that of lithium (Li) and a large charge / discharge capacity per unit mass. However, these electrode materials are being used up to near their theoretical charge / discharge capacity per unit mass, and the energy density per unit mass of the battery is approaching its limit. Therefore, in order to increase the utilization rate of the electrodes, research is underway to reduce conductive additives and binders that do not contribute to the discharge capacity.

[0004] Conductive additives play a role in forming conductive paths within the electrode, and it is required that these paths are resistant to breakage due to the expansion and contraction of the electrode film. To maintain conductive paths with a small amount of conductive additive, it is effective to use carbon materials with a large specific surface area, especially carbon nanotubes (CNTs), a type of nanocarbon. However, carbon materials with a large specific surface area have strong cohesive forces, making it difficult to uniformly disperse them in the composite slurry or electrode film.

[0005] Given this background, many methods have been proposed for producing carbon material dispersion compositions using various dispersants, and then manufacturing composite slurry via these carbon material dispersion compositions.

[0006] For example, Patent Documents 1 and 2 propose carbon material dispersion compositions with improved dispersibility by adding a basic compound along with polymer-based dispersants such as polyvinylpyrrolidone and hydrogenated nitrile rubber. However, while these dispersants can produce carbon material dispersion compositions with good dispersion, the dispersion state of the carbon material can become poor during the electrode film formation process, resulting in degraded conductivity.

[0007] Furthermore, Patent Documents 3 and 4 describe a predetermined Mooney viscosity (ML). 1+4 It has been proposed that carbon materials can be well dispersed in a composite slurry by using an electrode binder composition containing hydrogenated nitrile rubber having a specific surface area (100°C). Patent Document 5 proposes the use of a dispersant composition containing hydrogenated nitrile rubber with a weight-average molecular weight of 190,000 to 210,000 g / mol. However, these dispersants have low dispersibility, making it difficult to disperse carbon materials with large specific surface areas at high concentrations.

[0008] Therefore, Patent Document 6 proposes a technique that uses a copolymer having specific structural units and molecular weight as a dispersant to effectively disperse carbon materials in a solvent and maintain a good dispersion state when preparing the composite slurry and when manufacturing electrode films. However, obtaining a specific structure requires the addition of a large amount of base, which leads to problems such as a decrease in the molecular weight of the dispersant and / or a decrease in electrode strength due to the degradation of the binder resin. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2014-181140 [Patent Document 2] Korean Patent Registration No. 10-1831562

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, the problem to be solved by the present disclosure is to provide a resin composition capable of achieving both good dispersibility and good electrode characteristics, and a carbon material dispersion composition. Further, to obtain a composite slurry capable of obtaining an electrode film with high conductivity and adhesion, and more specifically, a secondary battery having excellent rate characteristics and cycle characteristics, and by having the secondary battery, to provide a vehicle with high safety and improved fuel efficiency.

Means for Solving the Problems

[0011] The inventors of the present invention have intensively studied to solve the above problems. The inventors of the present invention have found that the above problems can be solved by a copolymer (X) having a specific structure and a resin composition containing an alkali metal, when the resistivity of the resin composition when the non-volatile content is 8% by mass with N-methyl-2-pyrrolidone is in a specific range.

[0012] That is, the present disclosure includes the following embodiments. The embodiments of the present disclosure are not limited to the following. 〔1〕A resin composition comprising a copolymer (X) having an alkylene structural unit and a nitrile group-containing structural unit, and containing an alkali metal, wherein the content of the alkali metal is 50 ppm or more and less than 10,000 ppm, A resin composition wherein the resistivity of the resin composition when the non-volatile content is reduced to 8% by mass with N-methyl-2-pyrrolidone is 5,000 Ω·cm or more and 25,000 Ω·cm or less. [2] The resin composition according to [1], wherein the Z-average molecular weight of the copolymer (X) is 20,000 or more and 200,000 or less. [3] The resin composition according to [1] or [2], wherein the ratio (Mz / Mw) of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the copolymer (X) is 2.0 or less. A carbon material dispersion composition comprising a resin composition described in any of [1] to [3] and a carbon material. A composite slurry comprising the carbon material dispersion composition described in [5] and [4] and an active material. An electrode film obtained by coating with the asphalt slurry described in [6] and [5]. A secondary battery comprising an electrode having the electrode film described in [7] and [6] and an electrolyte. A vehicle equipped with the secondary battery described in [8] and [7]. [Effects of the Invention]

[0013] The resin composition disclosed herein exhibits excellent dispersibility of materials to be dispersed, such as carbon materials. By using a carbon material dispersion composition containing this resin composition, an electrode film with excellent conductivity and adhesion can be obtained. Furthermore, a secondary battery with excellent rate characteristics and cycle characteristics can be obtained. This makes it suitable for use in vehicle applications such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, where high capacity, high output, and high durability are required for the secondary battery. [Modes for carrying out the invention]

[0014] The following describes in detail the resin compositions, carbon material dispersion compositions, composite slurry, electrode films, and secondary batteries of this disclosure, but is not limited thereto. The numerical values ​​specified herein are those obtained by the methods disclosed in the embodiments or examples.

[0015] Furthermore, in this specification, numerical ranges specified using "~" include the numbers written before and after "~" as the lower and upper limits.

[0016] In this specification, "N-methyl-2-pyrrolidone" may be referred to as "NMP," "carbon black" as "CB," "carbon nanotube" as "CNT," and "carbon material dispersion composition" as "dispersion composition." Furthermore, non-volatile content refers to the solid content excluding the solvent, and is determined by measuring the amount of residue remaining after the solvent has evaporated or volatilized when the resin composition is heated above the boiling point of the solvent it contains.

[0017] In the embodiments of this disclosure, the resin composition refers to the state before the addition of the carbon material and the electrode active material, and the carbon material dispersion composition refers to the state before the addition of the electrode active material. In this respect, the resin composition and the carbon material dispersion composition are distinguished from composite slurry containing the electrode active material. Furthermore, this concept excludes situations where carbon material and electrode active material are intentionally added to the resin composition. Based on the amount of nonvolatile components in the resin composition (100% by mass), the carbon material and electrode active material may be 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less, or even 0% by mass. Furthermore, this concept excludes situations where electrode active material is intentionally added to a carbon material dispersion composition. Based on the amount of nonvolatile components in the carbon material dispersion composition (100% by mass), the amount of electrode active material may be 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less, or even 0% by mass. Unless otherwise noted, the various components mentioned herein may be used individually or in combination of two or more. The numerical values ​​specified herein are those obtained by the methods disclosed in the embodiments or examples.

[0018] ≪Resin composition≫ The resin composition of this embodiment contains a copolymer (X) having at least alkylene structural units and nitrile group-containing structural units, and an alkali metal. Furthermore, the alkali metal content is 50 ppm or more and less than 10,000 ppm, and when this resin composition is treated with N-methyl-2-pyrrolidone to achieve a non-volatile content of 8% by mass, its resistivity is 5,000 Ω·cm or more and 25,000 Ω·cm or less. This type of resin composition provides excellent dispersibility of the dispersed material and a stable dispersion composition. In particular, when the dispersed material is a carbon material, a carbon material dispersion composition with excellent dispersibility and oxidation resistance can be obtained, and since it also has excellent conductivity, secondary batteries using this composition can have excellent rate characteristics and high-temperature cycle characteristics.

[0019] In addition to the carbon materials described later, conventionally known inorganic pigments, organic pigments, etc., can be used as the dispersed material, but it can be used particularly effectively with carbon materials.

[0020] Examples of inorganic pigments include metal powders such as gold, silver, copper, silver-plated copper powder, silver-copper composite powder, silver-copper alloy, amorphous copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, and platinum; inorganic powders coated with these metals; metal oxide powders such as silver oxide, indium oxide, tin oxide, zinc oxide, and ruthenium oxide; inorganic powders coated with these metal oxides; and carbon nanotubes, carbon black, and graphite.

[0021] Examples of organic pigments include various pigments used in inks and the like. Such pigments include soluble azo pigments, insoluble azo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, perylene pigments, perinone pigments, dioxazine pigments, anthraquinone pigments, dianthaquinonyl pigments, anthrapyrimidine pigments, anthensrone pigments, indanthrone pigments, flavanthrone pigments, pyranthrone pigments, and diketopyrrolopyrrole pigments.

[0022] When the resin composition of this disclosure is modified with N-methyl-2-pyrrolidone to have a non-volatile content of 8% by mass, its resistivity is 5,000 Ω·cm or more and 25,000 Ω·cm or less. This type of resin composition allows for both good dispersibility and good electrode characteristics. Furthermore, to measure the resistivity, the non-volatile content of the resin composition can be measured in advance, and N-methyl-2-pyrrolidone can be added and mixed to achieve a non-volatile content of 8% by mass, thereby preparing a sample for liquid resistance measurement. The resistivity can be measured by the method described in the examples.

[0023] From the viewpoint of balancing the dispersibility of the dispersed material and the electrode resistance, the resistivity is preferably 5,000 Ω·cm to 20,000 Ω·cm, and more preferably 7,000 Ω·cm to 15,000 Ω·cm. The resistivity of a resin composition can be adjusted by controlling the molecular weight, molecular weight distribution, ion concentration, etc., of the copolymer by modifying the copolymer with a basic compound such as an alkali metal compound, or by applying shear stress to the copolymer. In this specification, the modification of a copolymer includes not only the modification of some of the structural units of the copolymer by hydrolysis, but also changes in the viscoelasticity and molecular weight of the copolymer.

[0024] The initial viscosity of the resin composition in this embodiment is preferably 10 mPa·s to 2,000 mPa·s, more preferably 100 mPa·s to 1,000 mPa·s, and even more preferably 100 mPa·s to 500 mPa·s, as measured using a B-type viscometer at 100 rpm and 25°C. Within this range, the resin composition can be made more stable. Furthermore, if the resin composition contains alkali metal compounds, the precipitation of alkali metal compounds is suppressed, resulting in superior stability.

[0025] (Copolymer(X)) Copolymer (X) is a copolymer having alkylene structural units and nitrile group-containing structural units. This copolymer may also have other structural units.

[0026] From the viewpoint of dispersibility of the dispersed material, the total content of alkylene structural units and nitrile group-containing structural units is preferably 50% by mass or more and 100% by mass or less, and more preferably 80% by mass or more, based on 100% by mass of copolymer (X). If copolymer (X) is a modified copolymer, from the viewpoint of dispersibility of the dispersed material, the total content of alkylene structural units and nitrile group-containing structural units is preferably 50% by mass or more and 100% by mass or less, based on 100% by mass of copolymer (X). Furthermore, if the nitrile group-containing structural units are modified by hydrolysis, the total content is preferably 50% by mass or more and 97% by mass or less, and more preferably 80% by mass or more and 95% by mass or less. The content of other structural units is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. When the copolymer has amide group-containing structural units that have been modified from nitrile group-containing structural units, the content of the amide group-containing structural units is preferably 5% by mass or less, and more preferably 3% by mass or less, based on 100% by mass of copolymer (X). If the content of the amide group-containing structural units is high, when the copolymer is dissolved in the electrolyte, the viscosity of the electrolyte may increase and the ionic conductivity may decrease significantly.

[0027] It is preferable to modify the copolymer (X) by adjusting the amount of basic compounds such as alkali metal compounds added, thereby controlling only the molecular weight or properties such as viscoelasticity while maintaining the composition.

[0028] A structural unit is a monomer incorporated into a polymer after polymerization. Unless otherwise specified, the content of structural units formed by the polymerization of monomers is usually equal to the ratio of monomers to the total monomers used in the polymerization of that polymer (the starting ratio). In other words, the content of each monomer relative to the total amount of monomers is taken as the content of each structural unit.

[0029] The copolymer (X) may be a modified copolymer obtained by adding a basic compound such as an alkali metal compound. When the nitrile groups contained in the nitrile group-containing structural units of the copolymer are modified by hydrolysis or the like, it is preferable that the content of alkylene structural units and nitrile group-containing structural units in the modified copolymer (X) is within the above range. The content of alkylene structural units and nitrile group-containing structural units can be calculated by IR measurement. For example, it can be calculated using the method described in ISO 14558:2016. Measurement can also be performed using the ATR method instead of the KBr tablet method. Using the above method, structural units and their content can be identified even in copolymers where copolymer (X) has been modified with a basic compound.

[0030] The number-average molecular weight (Mn) of the copolymer (X) in this embodiment is preferably 70,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. It is also preferably 10,000 or more. When the number-average molecular weight (Mn) of the copolymer (X) is within the above range, the copolymer is more likely to be adsorbed onto the dispersed material, and the dispersed material is more likely to be wetted by the solvent.

[0031] The weight-average molecular weight (Mw) of the copolymer (X) in this embodiment is preferably 20,000 to 180,000, more preferably 20,000 to 150,000, and even more preferably 20,000 to 100,000.

[0032] The average Z molecular weight (Mz) of copolymer (X) in this embodiment is preferably 20,000 to 250,000, more preferably 20,000 to 200,000, even more preferably 25,000 to 180,000, and particularly preferably 30,000 to 100,000.

[0033] When the weight-average molecular weight (Mw) and Z-average molecular weight (Mz) of copolymer (X) are within the above range, when a material to be dispersed, such as a carbon material, is included in the resin composition, not only is dispersion easier, but the viscosity of the resin composition is also lowered. Furthermore, this makes it possible to further improve the efficiency of removing metallic foreign particles contained in the resin composition using filters and magnets. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) are polystyrene-based values ​​and can be measured by gel permeation chromatography (GPC).

[0034] The average molecular weight Z is a weighted average using the square of the molecular weight as a weight, and is a value that is easily influenced by high molecular weight. The copolymer (X) has a molecular weight distribution, and the low molecular weight components function to improve the wettability of the dispersed material. The high molecular weight components, on the other hand, function to improve battery characteristics such as the viscosity stability of the dispersed material, the oxidation resistance of the copolymer, and the electrolyte dissolution resistance. By controlling the Z-average molecular weight of the copolymer (X) within the above range before adding the dispersed material, such as carbon material, to the resin composition, the viscosity of the resin composition can be lowered, the dispersed material becomes more easily wettable, and dispersion can proceed more easily. Furthermore, because the viscosity of the carbon material dispersion composition, as described later, is lower, the dispersion media moves more freely when using a dispersion machine that uses media such as a bead mill. Since the kinetic energy of the dispersion media is proportional to the mass and the square of the velocity of the dispersion media, efficiently moving the dispersion media in the carbon material dispersion composition not only allows for adjustment to the desired degree of dispersion, but also homogenizes the carbon material dispersion composition, resulting in a carbon material dispersion composition with excellent temporal stability and conductivity.

[0035] The average molecular weight (Mz) of copolymer (X) can be controlled by the synthesis conditions of copolymer (X) (composition, proportions, catalyst, reaction temperature, reaction time, etc.), modification of the copolymer, or by applying shear stress to the copolymer. For example, shear stress can be applied mechanically using a roll, kneader, etc., which can reduce the average molecular weight (Mz).

[0036] The polydispersity index (Mw / Mn) of the copolymer (X) in this embodiment is preferably 2.2 or less, more preferably 2.0 or less, and even more preferably 1.8 or less. Furthermore, 1.2 or more is preferred. When the polydispersity index (Mw / Mn) is within the above range, the ratio of low molecular weight components contained in the copolymer (X) is appropriate. In particular, when dispersing carbon materials, wetting of the dispersed material proceeds quickly, making dispersion easier. This allows for the acquisition of a carbon material dispersion composition while maintaining the structure of the carbon material, and makes it easier to obtain electrode films and secondary batteries with high conductivity and adhesion.

[0037] The ratio (Mz / Mw) of the weight-average molecular weight (Mw) to the Z-average molecular weight (Mz) of the copolymer (X) is preferably 2.2 or less, more preferably 2.0 or less, even more preferably 1.9 or less, and particularly preferably 1.8 or less. It is also preferably 1.5 or more, and more preferably 1.6 or more. When the ratio of the weight-average molecular weight (Mw) to the Z-average molecular weight (Mz) (Mz / Mw) is within the above range, the proportion of high molecular weight components contained in the copolymer (X) is appropriate, and a dispersion composition with good dispersion stability of the dispersed material is easily obtained.

[0038] The number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of the copolymer (X) can be adjusted, for example, by dispersing the copolymer with an amide-based polar solvent under high pressure. Alternatively, a resin composition containing an amide-based polar solvent may be dispersed under high pressure. For high-pressure dispersion, products such as Sugino Machine's "Starburst" can be used. In particular, the number-average molecular weight (Mn) is preferably prepared by dispersing the copolymer and an amide-based polar solvent under high pressure in the presence of an alkali metal.

[0039] [Alkylene structural unit] An alkylene structural unit is a structural unit containing an alkylene structure, and preferably a structural unit consisting solely of alkylene structures. The alkylene structure is preferably a linear alkylene structure or a branched alkylene structure. However, this excludes structural units that contain nitrile groups.

[0040] The alkylene structural unit preferably includes a structural unit represented by the following general formula (1A).

[0041] General formula (1A) [ka]

[0042] In general formula (1A), n represents an integer greater than or equal to 1. It is preferable that n is an integer greater than or equal to 2, and more preferably an integer greater than or equal to 3. It is preferable that n is an integer less than or equal to 5, and more preferably an integer less than or equal to 4. In particular, it is preferable that n is 3.

[0043] The alkylene structural unit preferably includes a structural unit represented by the following general formula (1B).

[0044] General formula (1B) [ka]

[0045] In general formula (1B), n represents an integer greater than or equal to 1. It is preferable that n is an integer less than or equal to 4, more preferably less than or equal to 3, and even more preferably less than or equal to 2. In particular, it is preferable that n is 2.

[0046] The method for introducing alkylene structural units into copolymers is not particularly limited, but examples include the following methods (1a) or (1b).

[0047] In method (1a), a copolymer is prepared by polymerization reaction using a monomer composition containing a conjugated diene monomer. The prepared copolymer contains monomer units derived from the conjugated diene monomer. In this disclosure, "monomer units derived from the conjugated diene monomer" may be referred to as "conjugated diene monomer units," and similarly, monomer units derived from other monomers may be omitted. Next, at least a portion of the conjugated diene monomer units are converted into alkylene structural units by hydrogenation. Hereinafter, "hydrogenation" may be referred to as "hydrogenation." The final copolymer contains units obtained by hydrogenating the conjugated diene monomer units as alkylene structural units.

[0048] Furthermore, the conjugated diene monomer unit includes at least one monomer unit having one carbon-carbon double bond. For example, the 1,3-butadiene monomer unit, which is a conjugated diene monomer unit, includes at least one monomer unit selected from the group consisting of monomer units having a cis-1,4 structure, monomer units having a trans-1,4 structure, and monomer units having a 1,2 structure, and may include two or more monomer units. In addition, the conjugated diene monomer unit may further include monomer units that do not have a carbon-carbon double bond and contain a branch point. In this specification, "branch point" refers to a branch point in a branched polymer, and when the conjugated diene monomer unit includes a monomer unit containing a branch point, the prepared copolymer and copolymer described above are branched polymers.

[0049] In method (1b), a copolymer is prepared by polymerization reaction using a monomer composition containing α-olefin monomers. The prepared copolymer contains α-olefin monomer units. The final copolymer contains α-olefin monomer units as alkylene structural units.

[0050] Among these, method (1a) is preferred because the copolymer can be easily produced. The number of carbon atoms in the conjugated diene monomer is 4 or more, preferably 4 to 6. Examples of conjugated diene monomers include conjugated diene compounds such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. Among these, 1,3-butadiene is preferred. The alkylene structural unit preferably includes structural units obtained by hydrogenating the conjugated diene monomer unit (hydrogenated conjugated diene monomer unit), and more preferably includes structural units obtained by hydrogenating the 1,3-butadiene monomer unit (hydrogenated 1,3-butadiene monomer unit). The conjugated diene monomer can be used individually or in combination of two or more types.

[0051] The hydrogenation method is preferably one that can selectively hydrogenate conjugated diene monomer units. Examples of hydrogenation methods include known methods such as the oil layer hydrogenation method or the aqueous layer hydrogenation method.

[0052] Hydrogenation can be carried out by conventional methods. For example, hydrogenation can be performed by treating a copolymer having conjugated diene monomer units, dissolved in a suitable solvent, with hydrogen gas in the presence of a hydrogenation catalyst. Examples of hydrogenation catalysts include nickel, palladium, rhodium, platinum, and copper.

[0053] In method (1b), the number of carbon atoms in the α-olefin monomer is 2 or more, preferably 3 or more, and more preferably 4 or more. The number of carbon atoms in the α-olefin monomer is preferably 6 or less, and more preferably 5 or less. Examples of α-olefin monomers include α-olefin compounds such as ethylene, propylene, 1-butene, and 1-hexene. The α-olefin monomer can be used alone or in combination of two or more.

[0054] The alkylene structural unit preferably includes at least one selected from the group consisting of structural units including linear alkylene structures and structural units including branched alkylene structures; more preferably includes at least one selected from the group consisting of structural units consisting only of linear alkylene structures and structural units consisting only of branched alkylene structures; and even more preferably includes at least one selected from the group consisting of structural units represented by formula (1A) and structural units represented by formula (1B).

[0055] The content of alkylene structural units is preferably 50% to 75% by mass, more preferably 55% to 70% by mass, and even more preferably 55% to 65% by mass, based on a total content of 100% by mass of alkylene structural units and nitrile group-containing structural units. By setting the content of alkylene structural units within the above range, the adsorption to the dispersed material and affinity to the dispersion medium can be controlled, allowing the dispersed material to exist stably in the dispersion medium. Furthermore, the affinity of the copolymer to the electrolyte can also be controlled, preventing problems such as the copolymer dissolving in the electrolyte within the battery and increasing the resistance of the electrolyte.

[0056] [Nitrile group-containing structural unit] The nitrile group-containing structural unit is a structural unit containing a nitrile group, preferably a structural unit containing an alkylene structure substituted with a nitrile group, and more preferably a structural unit consisting solely of an alkylene structure substituted with a nitrile group. The alkylene structure is preferably a linear or branched alkylene structure. The nitrile group-containing structural unit may further contain (or consist solely of) an alkyl structure substituted with a nitrile group. The number of nitrile groups contained in the nitrile group-containing structural unit is preferably one.

[0057] The nitrile group-containing structural unit preferably includes a structural unit represented by the following general formula (2A).

[0058] General formula (2A) [ka]

[0059] In general formula (2A), n represents an integer greater than or equal to 2. It is preferable that n is an integer less than or equal to 6, more preferably less than or equal to 4, and even more preferably less than or equal to 3. In particular, it is preferable that n is 2.

[0060] Nitrile group-containing structural units may include structural units represented by the following general formula (2B).

[0061] General formula (2B) [ka]

[0062] In general formula (2B), R represents a methyl group.

[0063] The method for introducing nitrile group-containing structural units into a copolymer is not particularly limited, but a method of preparing a copolymer by polymerization reaction using a monomer composition containing a nitrile group-containing monomer (method (2a)) can be preferably used. The copolymer ultimately obtained contains nitrile group-containing structural units as nitrile group-containing structural units. Examples of nitrile group-containing monomers that can form nitrile group-containing structural units include monomers containing a polymerizable carbon-carbon double bond and a nitrile group. For example, α,β-ethylenically unsaturated group-containing compounds having a nitrile group can be used, specifically acrylonitrile, methacrylonitrile, etc. In particular, from the viewpoint of increasing intermolecular forces between copolymers and / or between copolymers and dispersed substances (adsorbed substances), it is preferable that the nitrile group-containing monomer contains acrylonitrile. The nitrile group-containing monomer can be used alone or in combination of two or more types.

[0064] The content of nitrile group-containing structural units is preferably 25% by mass or more and 50% by mass or less, more preferably 30% by mass or more and 45% by mass or less, and even more preferably 35% by mass or more and 45% by mass or less, based on the total content of alkylene structural units and nitrile group-containing structural units of 100% by mass. By setting the content of nitrile group-containing structural units within the above range, the adsorption to the dispersed material and affinity to the dispersion medium can be controlled, and the dispersed material can be stably contained in the dispersion medium. Furthermore, the affinity of the resin composition to the electrolyte can also be controlled, preventing problems such as the resin composition dissolving in the electrolyte within the battery and increasing the resistance of the electrolyte.

[0065] [Other structural units] The structural units may have structural units other than alkylene structural units and nitrile group-containing structural units as necessary, to the extent that they do not impede the effects of this disclosure. Examples of other structural units include amide group-containing structural units and carboxyl group-containing structural units.

[0066] (Alkali metals) The resin composition of this disclosure contains an alkali metal. Furthermore, the alkali metal content in the resin composition is 50 ppm or more and less than 10,000 ppm. Preferably, the concentration is 500 ppm or more and 8000 ppm or less, and more preferably 2000 ppm or more and 5000 ppm or less. When the alkali metal content is within the above range, the adsorption to non-dispersed materials and affinity to the dispersion medium are improved when dispersed materials such as carbon materials are dispersed, resulting in improved dispersibility. Furthermore, if the amount of alkali metal in the resin composition is within the above range, it becomes easier to control the molecular weight of the copolymer (X) to an appropriate range by modifying it with an alkali metal compound as a basic compound or by applying shear stress to the copolymer, thereby improving the dispersibility of the dispersed material.

[0067] Alkali metals are included in the resin composition in the form of monomers used to synthesize the copolymer or copolymer (X) before modification, alkali metal compounds used to modify the copolymer, alkali metal compounds used as additives for pH adjustment, etc., or alkali metals contained in solvents, etc. In other words, the alkali metals contained in the resin composition include not only alkali metal compounds that have been intentionally added, but also alkali metals derived from the monomers used as raw materials, as well as catalysts, additives, solvents, etc.

[0068] Examples of alkali metals include elements such as lithium, sodium, and potassium. The alkali metal content in the resin composition can be determined by the method described in the examples using an ICP emission spectrometer.

[0069] (solvent) The resin composition of this embodiment preferably contains a solvent. Any solvent capable of dissolving the copolymer is acceptable, but an amide-based polar solvent is preferred. Examples of amide-based polar solvents include N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, and N-methylcaprolactam. Among these, it is more preferable to include at least one selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone.

[0070] (Method for manufacturing resin compositions) The method for producing the resin composition of this embodiment is not particularly limited, and the resin composition may be produced by any method. For example, one method involves preparing a copolymer by polymerization using a monomer composition containing a conjugated diene monomer and a nitrile group-containing monomer, and then hydrogenating the conjugated diene monomer units of the copolymer to obtain a resin composition containing copolymer (X). Alternatively, a polymer having alkylene structural units and nitrile group-containing structural units may be modified with a basic compound such as an alkyl metal compound, or subjected to shear stress to obtain a resin composition containing copolymer (X).

[0071] Furthermore, to obtain a copolymer with an alkali metal content of 50 ppm or more and less than 10,000 ppm, and a resistivity of 5,000 Ω·cm or more and 25,000 Ω·cm or less when the resin composition is reduced to a non-volatile content of 8% by mass using N-methyl-2-pyrrolidone, the following methods can be used in addition to the raw materials or blending amounts used to produce this copolymer. For example, the methods include: <1> A method of applying shear stress to an alkali metal copolymer using a pulverizer or the like. <2> A method in which an alkali metal or alkali metal compound is added to a copolymer to form a modified copolymer, and shear stress is applied using the aforementioned pulverizer. <3> One method involves applying shear stress to the copolymer using a pulverizer or the like, followed by the addition of an alkali metal or alkali metal compound. Among them, <2> or <3> This method is preferred, and it is especially preferable to use an alkali metal compound with a maximum particle size of 150 μm or less, particularly sodium hydroxide. By applying shear stress to the copolymer in the presence of an alkali metal compound with a maximum particle size of 150 μm or less, the finely dispersed alkali metal compound absorbs moisture, comes into contact with the copolymer, promotes the hydrolysis reaction of the copolymer, and allows for control of a structure, molecular weight, and molecular weight distribution suitable for dispersing the dispersed material.

[0072] <2> or <3> In this process, alkali metal compounds used to modify the copolymer can include, for example, alkali metal hydroxides or alkoxides. Preferably, alkali metal hydroxides are used.

[0073] In other words, the method for producing the resin composition preferably includes a step of mixing an alkali metal compound with a copolymer having alkylene structural units and nitrile group-containing structural units to produce a resin composition containing copolymer (X) and alkali metal.

[0074] In this case, the copolymer before modification is preferably a copolymer having alkylene structural units and nitrile group-containing structural units, mixed with an alkali metal compound, and having an alkali metal compound with an alkali metal compound having an alkali metal compound with an alkali metal compound having an alkali metal compound with an alkali metal compound having an alkali metal compound with an alkali metal compound having an alkali metal compound with an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having an alkali metal compound having a

[0075] To obtain a resin composition that satisfies the above requirements, it is preferable to dissolve the copolymer before modification in an amide-based polar solvent at a temperature of 60°C to 100°C. Furthermore, it is preferable to mix the alkali metal compound at a temperature of 40°C to 100°C, and more preferably at a temperature of 60°C to 80°C.

[0076] Examples of alkali metal compounds include alkali metal hydroxides or alkali metal alkoxides, with alkali metal hydroxides being preferred. Examples of alkali metal hydroxides that can be used include lithium hydroxide, sodium hydroxide, and potassium hydroxide. From the viewpoint of processability such as particle size control and handling, sodium hydroxide is preferred because it has excellent dispersion stability of the dispersed material. Sodium hydroxide is hygroscopic and can exhibit excellent effects when modifying some of the structural units of copolymers through hydrolysis or other means. Examples of alkali metal alkoxides that can be used include sodium ethoxide and sodium butoxide.

[0077] The alkali metal compound used to modify the copolymer preferably has a maximum particle size of 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. Furthermore, a particle size of 20 μm or more is preferred. When the maximum particle size of the alkali metal compound is within the above range, precipitation of the alkali metal compound in the resin composition is suppressed, resulting in superior stability of the resin composition. The settling rate of the alkali metal compound in the resin composition can be estimated using Stokes' equation, and the viscosity of the resin composition, along with the density and particle size of the alkali metal compound, are important for controlling the dispersion stability of the dispersed material. The maximum particle size of the alkali metal compound can be calculated, for example, by filtering through a filter with a known mesh size.

[0078] The particle size of alkali metal compounds is preferably controlled by grinding using conventionally known grinders, both dry and / or wet. Conventionally known grinders can be used for the grinding process. By setting the maximum particle size of the alkali metal compound within the above range, it is possible to appropriately control not only the composition and structure of the structural units constituting the copolymer (X), but also the changes in the molecular weight of the copolymer (X) due to modification. By controlling the molecular weight and molecular weight distribution of the copolymer (X) in this way, a dispersion composition with lower viscosity can be obtained when the dispersed material is dispersed. If the maximum particle size of the alkali metal compound is large, the alkali metal compound may precipitate in the resin composition, making it impossible to control the molecular weight of the copolymer. Furthermore, it may reduce the time-dependent stability of the carbon material dispersion composition and composite slurry described later.

[0079] A grinder is a device that applies forces such as compression, impact, shear, and friction to a sample to make it finer. Various grinders can be used to control particle size, including mortars, pin mills, hammer mills, pulperizers, attritors, jet mills, cutter mills, ball mills, bead mills, colloid mills, conical mills, disc mills, edge mills, Wonder Crushers, vibrating mills, ultrasonic homogenizers, and high-shear mixers.

[0080] To control the alkali metal content and predetermined resistivity of the resin composition, it is preferable to use the copolymer before modification dissolved in a solvent at a temperature of 60°C to 100°C. In a more preferable embodiment, the resin composition containing the solvent may contain copolymer (X) in an amount of 1 to 50, 2 to 40, 5 to 30, or 10 to 20% by mass relative to the total amount of the resin composition. In a more preferable embodiment, the solvent may contain an amide-type polar solvent. Furthermore, in order to obtain a resin composition that satisfies the above requirements, it is preferable to use the alkali metal compound dissolved in a solvent at a temperature of 40°C to 100°C or 60°C to 80°C. In a more preferable embodiment, the resin composition containing the solvent may contain alkali metal compound in an amount of 0.1 to 20% by mass, 0.5 to 10% by mass, 1 to 8% by mass, or 2 to 5% by mass relative to the total amount of the resin composition. By ensuring that both copolymer (X) and alkali metal compound satisfy these ranges relative to the total amount of the resin composition, the alkali metal content and predetermined resistivity of the resin composition can be controlled more easily.

[0081] To control the alkali metal content and desired resistivity of a resin composition, it is advisable to add an alkali metal compound in the resin composition manufacturing method. In this case, one method of manufacturing the resin composition involves dissolving the copolymer (X) and the alkali metal compound in a solvent and then mixing them. In this case, it is even better to prepare the copolymer (A) dissolved in the solvent and the alkali metal compound dissolved in the solvent separately and then mix them. An amide-based polar solvent is suitable as the solvent.

[0082] To control the alkali metal content and predetermined resistivity of a resin composition, as described above, there is a method of controlling the amount and method of adding alkali metal compounds in the resin composition manufacturing method. This method allows for control of the alkali metal content in the resulting resin composition, as well as control of the predetermined resistivity.

[0083] Another method for controlling the alkali metal content and predetermined resistivity of a resin composition is to control the molecular weight and molecular weight distribution of the copolymer (X). For example, even if the alkali metal content is low and the predetermined resistivity is high, the increase in the predetermined resistivity can be suppressed by reducing the molecular weight of the copolymer (X). Preferably, the number average molecular weight Mn of the copolymer (X) is 70,000 or less, 60,000 or less, or 50,000 or less. In another embodiment, preferably, the Mw / Mn of the copolymer (X) is 2.60 or less, 2.50 or less, or 2.40 or less. In a more preferable embodiment, when the Mw / Mn of the copolymer (X) is 2.60 or less, 2.50 or less, or 2.40 or less, the Z average molecular weight Mz is 400,000 or less, 300,000 or less, or 250,000 or less. Some methods for controlling these molecular weights and molecular weight distributions include controlling the mixing time between the copolymer (X) and the alkali metal compound, the amount of alkali metal compound used, the respective content of the copolymer (X) and alkali metal compound relative to the total resin composition, and the number of passes when using a pass-type dispersion apparatus.

[0084] ≪Carbon Material Dispersion Composition≫ The carbon material dispersion composition of this embodiment comprises at least a carbon material and the resin composition of this embodiment. Preferably, it also contains a solvent. Including a solvent in the carbon material dispersion composition makes it easier to obtain a carbon material dispersion composition with good dispersion.

[0085] (Carbon materials) As carbon materials, various types of carbon black can be used, such as acetylene black, furnace black, hollow carbon black, channel black, thermal black, and Ketjen black. In addition, amorphous carbonaceous materials such as oxidized carbon black, graphitized carbon black, mesophase carbon black, soft carbon, and hard carbon, as well as carbon fibers such as carbon nanotubes or carbon nanofibers and vapor-grown carbon fibers, can also be used. In particular, it is preferable to include at least one selected from the group consisting of carbon black and carbon fibers, and especially preferable to include carbon nanotubes.

[0086] The carbon purity of the carbon material is preferably 95% by mass or higher, and more preferably 97% by mass or higher, based on the mass of the carbon material (with the mass of the carbon material being 100% by mass).

[0087] Carbon nanotubes have a structure in which planar graphite is wound into a cylindrical shape, and include single-walled carbon nanotubes and multi-walled carbon nanotubes, and these may be mixed together. Among these, the inclusion of multi-walled carbon nanotubes is preferred. Multi-walled carbon nanotubes have a structure in which two or more layers of graphite are wound, while single-walled carbon nanotubes have a structure in which a single layer of graphite is wound. The sidewalls of carbon nanotubes do not have to be graphite structures. For example, carbon nanotubes having sidewalls with an amorphous structure can also be used as carbon materials.

[0088] The average outer diameter of the carbon nanotubes is preferably between 1 nm and 25 nm, more preferably between 3 nm and 20 nm, and even more preferably between 4 nm and 15 nm. When the average outer diameter is within the above range, a good conductive network is easily formed within the electrode, and the active material inside the secondary battery is utilized uniformly during charging and discharging, thereby suppressing degradation of the active material and further improving the cycle characteristics of the secondary battery.

[0089] The BET specific surface area of the carbon nanotube is preferably 100 m 2 / g or more and 1000 m 2 / g or less, more preferably 200 m 2 / g or more and 700 m 2 / g or less. When the BET specific surface area is within the above range, an efficient conductive network can be formed with a small amount, and the amount of conductive material in the electrode can be reduced. As a result, the degree of freedom in battery design, such as increasing the amount of active material and binder resin, is increased. Furthermore, during the preparation of the composite slurry, the composite of the active material and the carbon nanotube is likely to proceed, so it is easy to obtain an electrode film having a homogeneous conductive network in which the surface of the active material is covered with carbon nanotubes, suppressing the electrolyte decomposition reaction at the interface between the electrolyte and the active material, and improving the cycle characteristics of the battery. The BET specific surface area can be measured by the BET method described in JIS Z 8830:2013.

[0090] The G / D ratio (peak ratio of G-band and D-band) of the carbon nanotube is the maximum peak intensity within the range of 1560 cm -1 ~1600 cm -1 designated as G, and the maximum peak intensity within the range of 1310 cm -1 ~1350 cm -1 designated as D. When the G / D ratio is preferably 0.5 to 10, more preferably 0.7 to 4.5. When the G / D ratio of the carbon nanotube is within the above range, the contact resistance between the carbon nanotubes is considered to be small, and good conductivity is likely to be obtained. Also, it is presumed that the amount of functional groups on the surface of the multi-walled carbon nanotube is appropriate, the affinity with the solvent is good, and the dispersibility is better.

[0091] The volume resistivity of the carbon nanotube is preferably 1.0×10 -2 Ω·cm to 3.0×10 -2 Ω·cm, more preferably 1.0×10 -2 Ω·cm to 2.0×10 -2 Ω·cm. The volume resistivity of carbon nanotubes can be measured using a powder resistivity measuring device (Mitsubishi Chemical Analytech Co., Ltd.: Rolester GP Powder Resistivity Measuring System MCP-PD-51). When the volume resistivity is within the above range, the conductivity of the electrode film tends to be good, making it easier to obtain a secondary battery with excellent rate characteristics and cycle characteristics.

[0092] It is preferable that the carbon nanotubes have had metallic impurities removed by magnetic force using electromagnets. For example, it is preferable to remove metallic impurities by setting up electromagnets in the crushing or filling process of the carbon nanotubes and passing the carbon nanotubes through them. The carbon purity of the carbon nanotubes is preferably as high as possible, preferably 98.0% by mass or more out of 100% by mass of carbon nanotubes, more preferably 99.5% by mass or more, even more preferably 99.8% by mass or more, and particularly preferably 99.9% by mass or more. In other words, the content of metallic foreign particles is preferably as low as possible, preferably 2.0% by mass or less per 100% by mass of carbon nanotubes, more preferably 0.5% by mass or less, even more preferably 0.2% by mass or less, and particularly preferably 0.1% by mass or less. By using carbon nanotubes produced by a manufacturing method that does not use a metal catalyst as a core, or carbon nanotubes obtained by conventionally known purification methods such as acid treatment, the content of metal foreign particles can be reduced to 0.5% by mass or less per 100% by mass of carbon nanotubes, thereby improving the various properties of secondary batteries. The carbon purity of carbon nanotubes can be determined using an ICP emission spectrometer by the method described in the examples.

[0093] The solvent is not particularly limited as long as it is miscible with the resin composition of this embodiment, but it is preferably capable of dissolving the resin composition, more preferably a high dielectric constant solvent, and preferably contains a solvent consisting of one of any high dielectric constant solvents, or a mixed solvent consisting of two or more. Alternatively, one or more other solvents may be mixed with the high dielectric constant solvent and used.

[0094] As high dielectric constant solvents, amides (N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylcaprolactam, etc.), heterocyclic solvents (cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, etc.), sulfoxide solvents (dimethyl sulfoxide, etc.), sulfone solvents (hexamethylphosphorotriamide, sulfolane, etc.), lower ketone solvents (acetone, methyl ethyl ketone, etc.), carbonate solvents (diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, propylene carbonate, ethylene carbonate), and others such as tetrahydrofuran, urea, and acetonitrile can be used. The dispersion medium preferably contains an amide-based polar solvent, and more preferably contains at least one selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone. The relative permittivity of the high dielectric constant solvent can be the value described in the solvent handbook, and is preferably 2.5 or higher at 20°C. By using a high dielectric constant solvent, the interaction between the nitrile groups contained in the resin composition of this embodiment, the carbon material, and the solvent can be enhanced.

[0095] The water content in the solvent is preferably 100 ppm to 1500 ppm, and more preferably 100 ppm to 1000 ppm. When the water content is within this range, the alkali metal contained in the resin composition of this embodiment dissolves in the carbon material dispersion composition, and the dispersion stability of the carbon material dispersion composition tends to be good.

[0096] The solvent content in this embodiment is preferably 90% to 99% by mass, and more preferably 92% to 98% by mass, based on the mass of the carbon material dispersion composition (with the mass of the carbon material dispersion composition being 100% by mass). When the content is within the above range, a fluid carbon material dispersion composition is easily obtained, and a carbon material dispersion composition with excellent dispersion stability is easily obtained. By using a carbon material dispersion composition with excellent dispersion stability, an electrode film with stable conductivity can be obtained, and the quality of the secondary battery can be easily stabilized.

[0097] To obtain the carbon material dispersion composition of this embodiment, it is preferable to perform a process in which the carbon material is dispersed in a solvent. The dispersion apparatus used for such a process is not particularly limited.

[0098] As the dispersion device, a disperser commonly used for pigment dispersion, etc., can be used. For example, either a medialess disperser or a media-type disperser may be used. Examples of medialess dispersers include mixers such as dispersers, homomixers, and planetary mixers; homogenizers (such as Branson's Advanced Digital Sonifer®, MODEL 450DA, M-Technic's "Clearmix", PRIMIX's "Filmix", Silverson's "Abramix", etc.); paint conditioners (Red Devil), colloid mills (PUC's "PUC Colloid Mill", IKA's "Colloid Mill MK"), and cone mills (such as IKA's "Cone Mill MKO"). Examples of media-type dispersers include ball mills, sand mills (such as Shinmaru Enterprises' "Dino Mill"), attritors, pearl mills (such as Eirich's "DCP Mill"), ball mills, bead mills (Mugen Flow®, manufactured by Ashizawa Finetech), and media-type paint conditioners. Furthermore, examples include high-pressure homogenizers (such as Genus's "Genus PY", Sugino Machine's "Starburst", and Nanomizer's "Nanomizer"), media-less dispersers such as M-Technique's "CREA SS-5" and Nara Machinery's "MICROS", and other roll mills. Dispersers are not limited to these.

[0099] The carbon material content in the carbon material dispersion composition is preferably 1% by mass or more and 20% by mass or less, based on the mass of the carbon material dispersion composition (with the mass of the carbon material dispersion composition being 100% by mass), more preferably 2% by mass or more and 15% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less.

[0100] The amount of dispersant contained in the carbon material dispersion composition is preferably 5% to 100% by mass, more preferably 10% to 75% by mass, and even more preferably 20% to 50% by mass, based on the mass of the carbon material (with the mass of the carbon material being 100% by mass). When the amount of dispersant is within the above range, the dispersion stability of the carbon material in the carbon material dispersion composition tends to be good. In addition, the peel strength of the electrodes for secondary batteries is good.

[0101] The carbon material dispersion composition preferably has a moisture content of 100 ppm to 1500 ppm, and more preferably 200 ppm to 1000 ppm. When the moisture content of the carbon material dispersion composition is within the above range, gelation of the composite slurry described later is suppressed, making it easier to obtain a composite slurry and electrode film of stable quality.

[0102] The initial viscosity of the carbon material dispersion composition of this embodiment is preferably 100 mPa·s to 2,000 mPa·s, and more preferably 200 mPa·s to 1,000 mPa·s, as measured using a B-type viscometer at 25°C and 100 rpm. When the initial viscosity of the carbon material dispersion composition is within the above range, it is considered that the dispersion state of the carbon material contained in the carbon material dispersion composition is appropriate and that it is easy to form a conductive network.

[0103] The viscosity of the carbon material dispersion composition of this embodiment after storage for one week at 60°C is preferably 500 mPa·s to 6,000 mPa·s, more preferably 500 mPa·s to 3,000 mPa·s, and even more preferably 500 mPa·s to 2,000 mPa·s after cooling to 25°C and measuring with a B-type viscometer at 25°C and a rotor rotation speed of 100 rpm.

[0104] Carbon material dispersion compositions with a viscosity within the above range are considered to have appropriate compositional ratios of carbon material, resin composition, and solvent, as well as a suitable dispersion process, and thus exhibit good dispersion stability. Since the adsorption reaction of the resin composition contained in the carbon material dispersion composition to the carbon material surface is an endothermic reaction, the amount of resin composition necessary and sufficient to obtain a carbon material dispersion composition with excellent dispersion stability can be determined by evaluating the viscosity of the carbon material dispersion composition after storage under high-temperature conditions.

[0105] In this embodiment, it is preferable to use a carbon material dispersion composition from which metallic foreign matter has been removed by a filter or magnet.

[0106] [Process for removing metallic foreign particles] The method for removing metallic foreign particles is not particularly limited, but examples include a filtration process using a filter and a magnetic separation process such as magnetic separation using an electromagnet. It is preferable to include a filtration step and a magnetic separation step, because the magnetic separation step can remove metallic foreign particles contained in the carbon material, and the filtration step can recover metallic foreign particles that cannot be removed by magnets. Furthermore, it is more preferable to perform a magnetic separation process after the filtration process. Performing a filtration process at the end before shipment of the carbon material dispersion composition can also remove metallic foreign particles from pipes and the like.

[0107] (Magnetic selection process) Various conventionally known methods can be used to remove metal foreign particles using magnetic force in a magnetic separation process. In particular, it is preferable to use a method in which an electromagnet is set up during the manufacturing process of the carbon material dispersion composition and the carbon material dispersion composition is passed through it to remove metal foreign particles.

[0108] The magnetic flux density of the electromagnet is preferably between 5,000 gauss and 20,000 gauss, and more preferably between 10,000 gauss and 20,000 gauss. By using an electromagnet within the above range, it is possible to remove not only metallic foreign particles contained in the carbon material, but also metallic foreign particles generated during the manufacturing process.

[0109] Specifically, for example, you can use CS-150HHH, CS-250HHH, CS-300HHH from Nippon Magnetics Co., Ltd., DVF-50-6, DVF-50-9, DVF-50-12 from Nippon Elise Magnetics Co., Ltd., and EMF-100S, EMF-150S, EMF-250S, EMF-300S from Taiho Magnetic Co., Ltd.

[0110] The flow velocity of the carbon material dispersion composition when it comes into contact with the electromagnet is preferably 1 L / min or more and 300 L / min or less, and preferably 30 L / min or more and 200 L / min or less.

[0111] It is preferable that the carbon material dispersion composition passes through the electromagnet three or more times. If it passes through fewer times, there is a possibility that metallic foreign particles cannot be removed. When passing through the electromagnet in a circulating manner, it is preferable to pass it through more times, taking into account the uniformity within the tank used in the manufacturing process.

[0112] (filtration process) For filtering out metallic foreign particles, a surface filter such as a membrane filter or a depth filter may be used, but a depth filter is more preferred. Since metallic foreign particles are not spherical and are often oriented, using a depth filter allows for efficient removal of metallic foreign particles from the carbon material dispersion composition.

[0113] Unlike surface filters (filters that primarily capture particulate matter in a fluid on their surface), depth filters primarily capture particulate matter in a fluid within the filter medium, and are characterized by high particle retention performance and resistance to clogging. By using depth filters, metallic foreign particles in carbon material dispersion compositions can be removed more selectively.

[0114] For example, 3M™ PP nonwoven fabric depth cartridges from the NT-T series can be used as depth filters.

[0115] The filtration accuracy of the filter is preferably 5 μm to 50 μm, and more preferably 10 μm to 40 μm. If a filter with a small pore size is used to increase the removal rate of metal foreign particles in the carbon material dispersion composition, clogging of the carbon material may reduce the removal efficiency of metal foreign particles. On the other hand, when a carbon material dispersion composition filtered within the above range is filtered, the removal efficiency of metal foreign particles is high, making it easier to obtain a carbon material dispersion composition with fewer metal foreign particles.

[0116] ≪Asphalt mixture slurry≫ The composite slurry of this embodiment comprises a carbon material dispersion composition and an active material. That is, it comprises at least the resin composition of this disclosure, a carbon material, and an active material, and preferably further comprises a binder resin.

[0117] A binder resin is a resin used to bond carbon materials together. There are no particular restrictions on the binder resin, but examples include polymers or copolymers containing fluororesins, ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinylpyrrolidone, etc. as constituent units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluororesins; cellulose resins such as carboxymethylcellulose; rubbers such as styrene-butadiene rubber; and conductive resins such as polyaniline and polyacetylene. In particular, using fluororesin as the binder resin is preferable from the viewpoint of electrochemical oxidation-reduction resistance.

[0118] For the fluororesin in this embodiment, polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene are preferred, for example.

[0119] The weight-average molecular weight of the fluororesin is preferably 10,000 to 2,000,000, more preferably 100,000 to 1,000,000, and particularly preferably 200,000 to 1,000,000.

[0120] Active material refers to the material that forms the basis of a battery reaction. Active material can be divided into positive electrode active material and negative electrode active material based on its electromotive force. In this specification, positive electrode active material and negative electrode active material may sometimes be simply referred to as "active material."

[0121] The positive electrode active material is not particularly limited, but can be metal oxides, metal sulfides, and other metal compounds that can be doped or intercalated with lithium ions or sodium ions, as well as conductive polymers. Examples include oxides of transition metals such as Fe, Co, Ni, and Mn, complex oxides with lithium and sodium, inorganic compounds such as transition metal sulfides, polyanionic compounds, and Prussian blue compounds. Specifically, MnO, V2O5, V6O 13 Examples include transition metal oxide powders such as TiO2, lithium-transition metal composite oxide powders such as layered lithium nickelate, lithium cobaltate, lithium manganate, and spinel-structured lithium manganate, lithium iron phosphate-based materials which are olivine-structured phosphoric acid compounds, transition metal sulfide powders such as TiS2 and FeS, layered sodium ironate, sodium manganate, sodium chromate, sodium nickelate, and sodium iron phosphate-based materials which are olivine-structured phosphoric acid compounds. Conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Furthermore, the above inorganic and organic compounds may be mixed and used.

[0122] The positive electrode active material is preferably a composite oxide of lithium containing a transition metal such as Al, Fe, Co, Ni, or Mn; more preferably a composite oxide of lithium containing any one of Al, Co, Ni, or Mn; and particularly preferably a composite oxide of lithium containing Ni and / or Mn. When these active materials are used, particularly good effects can be obtained.

[0123] The negative electrode active material is not particularly limited as long as it can be doped or intercalated with lithium or sodium ions. For example, metal Li, alloy systems such as its alloys, tin alloys, silicon alloys, lead alloys, etc., LiXFe2O3, LiXFe3O4, LiXWO2 (x is a number between 0 < x < 1), metal oxide systems such as lithium titanate, lithium vanadate, lithium silicate, conductive polymer systems such as polyacetylene, poly-p-phenylene, amorphous carbonaceous materials such as soft carbon, hard carbon, artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite, carbon black, mesophase carbon black, resin-fired carbon materials, gas-phase grown carbon fibers, carbon fiber and other carbon-based materials. These negative electrode active materials can be used alone or in combination of two or more.

[0124] The BET specific surface area of the active material is preferably 0.1 m 2 / g or more and 10 m 2 / g or less, more preferably 0.2 m 2 / g or more and 5 m 2 / g or less, and even more preferably 0.3 m 2 / g or more and 3 m 2 / g or less.

[0125] The average particle size of the active material is preferably in the range of 0.05 μm to 100 μm, and more preferably in the range of

[0126] 0.1 μm to 50 μm. The average particle size of the active material as referred to in this specification is the average value of the particle sizes measured by an electron microscope for the active material.

[0126] To obtain the composite material slurry of this embodiment, it is preferable to perform a dispersion treatment after adding the active material to the carbon material dispersion composition. The dispersion device used for performing such treatment is not particularly limited. The composite material slurry can be obtained using the dispersion device described for the above carbon material dispersion composition.

[0127] The content of the active material in the asphalt slurry is preferably 20% to 85% by mass, and particularly preferably 40% to 85% by mass, based on 100% by mass of the asphalt slurry.

[0128] The carbon material content in the composite slurry is preferably 0.05% to 10% by mass, more preferably 0.1% to 5% by mass, and more preferably 0.1% to 3% by mass, based on 100% by mass of the active material.

[0129] The binder resin content in the asphalt slurry is preferably 0.5% to 20% by mass, more preferably 1% to 10% by mass, and particularly preferably 1% to 5% by mass, based on 100% by mass of the active material.

[0130] The solid content concentration of the asphalt slurry is preferably 30% to 90% by mass, and more preferably 40% to 85% by mass, based on 100% by mass of the asphalt slurry.

[0131] The moisture content in the asphalt slurry is preferably 500 ppm or less, more preferably 300 ppm or less, and particularly preferably 100 ppm or less.

[0132] ≪Electrode≫ The electrode film of this embodiment comprises a current collector and an electrode film formed from an asphalt slurry. The electrode film is a coating film of asphalt slurry. For example, it is a coating film formed by coating and drying an asphalt slurry onto a current collector to create an electrode asphalt layer.

[0133] The material and shape of the current collector used in the electrode film of this embodiment are not particularly limited, and can be appropriately selected to suit various secondary batteries. For example, the material of the current collector can be a metal or alloy such as aluminum, copper, nickel, titanium, or stainless steel. In terms of shape, a flat foil is generally used, but current collectors with roughened surfaces, perforated foils, and mesh shapes can also be used.

[0134] There are no particular limitations on the method for applying the asphalt slurry onto the current collector to form an electrode film, and known methods can be used. Specifically, die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, or electrostatic coating methods can be used, and drying methods such as standing drying, forced-air drying, hot-air drying, infrared heating, and far-infrared heating can be used, but are not limited to these.

[0135] Furthermore, rolling treatment using a flatbed press or calender roll may be performed after coating. The thickness of the electrode composite layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

[0136] ≪Secondary battery≫ The secondary battery of this embodiment comprises an electrode having the electrode film of this disclosure and an electrolyte. The carbon material dispersion composition using the resin composition of this embodiment has excellent rate characteristics because it forms a good conductive network within the secondary battery electrode, and the active material is utilized homogeneously during charging and discharging, so degradation of the active material is less likely to occur. Furthermore, overcharging and over-discharging during charging and discharging are suppressed. As a result, degradation of battery characteristics due to electrolyte decomposition and metal deposition is less likely to occur, and the battery has excellent cycle characteristics.

[0137] As the positive electrode, an electrode film can be prepared by coating a slurry containing the positive electrode active material onto a current collector and drying it.

[0138] As the negative electrode, an electrode film can be prepared by coating and drying a slurry containing the negative electrode active material onto the current collector.

[0139] Various conventionally known electrolytes that allow ion movement can be used. For example, lithium salts such as LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, Li(CF3SO2)3C, LiI, LiBr, LiCl, LiAlCl, LiHF2, LiSCN, or LiBPh4 (where Ph is a phenyl group) can be used, but are not limited to these, and sodium salts can also be used. It is preferable to dissolve the electrolyte in a non-aqueous solvent and use it as an electrolyte solution.

[0140] Non-aqueous solvents are not particularly limited, but examples include carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone; glycines such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and nitriles such as acetonitrile. These solvents may be used individually or in combination of two or more.

[0141] The secondary battery of this embodiment preferably includes a separator. Examples of separators include polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyamide nonwoven fabric, and those treated to be hydrophilic, but are not limited to these.

[0142] The structure of the secondary battery in this embodiment is not particularly limited, but it typically consists of a positive electrode, a negative electrode, and a separator provided as needed, and can be in various shapes depending on the intended use, such as paper type, cylindrical type, button type, or laminated type.

[0143] The secondary battery of this embodiment is not particularly limited in its use, and can be used specifically as a power source for consumer electronics such as mobile phones, laptop computers, and digital cameras; as an emergency power source for hospitals, factories, and buildings; and for vehicles such as hybrid cars, plug-in hybrid cars, electric cars, electric assist bicycles, and railway vehicles. The secondary battery, for example, recovers regenerative energy from the power of a vehicle.

[0144] In particular, because it is a secondary battery with high charge / discharge performance and excellent cycle characteristics, it can be suitably used in vehicles, resulting in vehicles that are highly safe and can be expected to improve fuel efficiency. Furthermore, it can demonstrate excellent performance even in vehicle applications where high-current charging and discharging are desired.

[0145] The mounting location of the secondary battery in the vehicle of this embodiment is not particularly limited. For example, when the secondary battery is installed in an automobile, it can be installed in the engine compartment, at the rear of the vehicle, or under the seats. [Examples]

[0146] The present disclosure will be further explained by the following examples. The present disclosure is not limited to the following examples unless it exceeds its gist. Unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "percentage by mass". The amounts in the table are in parts by mass. Blank spaces in the table indicate that an ingredient is not included.

[0147] The materials used in the examples and comparative examples are shown below. Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, liquid hydrogenated nitrile butadiene rubber, number average molecular weight 20,000, weight average molecular weight 35,000, Z average molecular weight 60,000, alkylene structural units 66% by mass, nitrile group-containing structural unit content 34% by mass), hereinafter referred to as HNBR1. Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, ZN35052, Mooney viscosity 20, number average molecular weight 48,000, weight average molecular weight 110,000, Z average molecular weight 210,000, alkylene structural units 66% by mass, nitrile group-containing structural unit content 34% by mass), hereafter referred to as HNBR2. Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, ZN35053, Mooney viscosity 35, number average molecular weight 53,000, weight average molecular weight 133,000, Z average molecular weight 270,000, alkylene structural units 64% by mass, nitrile group-containing structural unit content 36% by mass), hereafter referred to as HNBR3. Hydrogenated nitrile butadiene rubber (manufactured by Zannan Scitech, ZN35056, Mooney viscosity 65, number average molecular weight 75,000, weight average molecular weight 183,000, Z average molecular weight 364,000, alkylene structural units 64% by mass, nitrile group-containing structural unit content 36% by mass), hereafter referred to as HNBR4. Hydrogenated nitrile butadiene rubber (manufactured by ARLANXEO, Thermon(R) 3406, Mooney viscosity 63, number average molecular weight 78,000, weight average molecular weight 209,000, Z average molecular weight 434,000, alkylene structural units 66% by mass, nitrile group-containing structural unit content 34% by mass)), hereafter referred to as HNBR5. • Carbon nanotubes (JEIO-made, JENOTUBE6A, average outer diameter 6nm, BET specific surface area 650m²) 2 ( / g) Below, CNT1 is used. • Carbon nanotubes (JEIO manufactured, JENOTUBE10B, average outer diameter 10 nm, BET specific surface area 230 m²) 2 ( / g) Below, we will refer to it as CNT2. • HS-100: Denka Black HS-100 (manufactured by Denka Corporation, acetylene black, average primary particle size 48nm, BET specific surface area 39m²) 2 ( / g) Below this, we will refer to it as CB1.

[0148] The methods for measuring the physical properties of the materials used in each example and comparative example are as follows.

[0149] <Specific surface area> The BET specific surface area of ​​carbon nanotubes and carbon black can be measured by the BET method using nitrogen adsorption measurement, in accordance with JIS Z 8830:2013.

[0150] <Average outer diameter> The average outer diameter of carbon nanotubes can be calculated by observing and imaging carbon nanotubes using a transmission electron microscope, then selecting 300 random carbon nanotubes from the resulting images and measuring their respective outer diameters. Similarly, the average primary particle diameter of carbon black can be calculated by first observing and imaging carbon black using a transmission electron microscope, then selecting 100 random spherical carbon black primary particles from the resulting images and measuring their respective outer diameters.

[0151] <Moony viscosity> The Mooney viscosity of hydrogenated nitrile butadiene rubber was measured at 100°C using an L-type rotor in accordance with the Japanese Industrial Standard JIS K6300-1 (ML1+4, 100°C).

[0152] <Fabrication of standard negative electrodes> In a 150ml plastic container, 0.5 parts by mass of acetylene black (Denka Black® HS-100, manufactured by Denka), 1 part by mass of MAC500LC (carboxymethylcellulose sodium salt, Sunrose special type MAC500L, manufactured by Nippon Paper Industries, 100% non-volatile content), and 98.4 parts by mass of water were added. The mixture was then stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Sinky Awatori Rentaro, ARE-310). Furthermore, 92 parts by mass of artificial graphite (manufactured by Nippon Graphite Industry, CGB-20) and 5 parts by mass of silicon oxide (manufactured by Osaka Titanium Technology, SILICON MONOOXIDE SiO 1.3C 5μm, 100% non-volatile content) were added as active materials, and the mixture was stirred at 3000 rpm for 10 minutes using a high-speed stirrer. Next, 3.1 parts by mass of styrene-butadiene rubber (SBR, TRD2001, manufactured by JSR Corporation) were added, and the mixture was stirred at 2000 rpm for 30 seconds using the above-mentioned rotating / revolving mixer to obtain a negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was measured using an applicator to obtain a basis weight of 8 mg / cm³ per unit area of ​​the electrode. 2 After coating the copper foil in this manner, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes. Furthermore, it was rolled using a roll press (manufactured by Sankumetal Co., Ltd., 3t hydraulic roll press) to obtain a density of 1.6 g / cm³ in the asphalt layer. 3 A standard negative electrode was fabricated.

[0153] <Preparation of alkali metal compound dispersions> Capacity 2000cm 3 950 parts by mass of NMP and 50 parts by mass of NaOH (sodium hydroxide, manufactured by Tosoh Corporation, Tosoh Pearl) were added to a plastic container. A fine emulsion screen was attached to a high-share mixer (L5M-A, manufactured by Silverson), and the mixture was dispersed at a speed of 9000 rpm until the mixture was uniform. Then, using a filtration bell, the mixture was passed through a nylon filter with a mesh size of 150 μm to prepare an NaOH dispersion (NaOH concentration 5% by mass). The maximum particle size of sodium hydroxide was 150 μm or less.

[0154] ≪Methods for measuring and evaluating physical properties≫ The methods for measuring and evaluating the physical properties of the resin compositions, carbon material dispersion compositions, electrode films, and secondary batteries used in the examples and comparative examples described below are as follows.

[0155] <Measurement of number-average molecular weight, weight-average molecular weight, and Z-average molecular weight of copolymers> (Preparation of samples for molecular weight measurement) To measure the number-average molecular weight (Mn), weight-average molecular weight (Mw), and Z-average molecular weight (Mz) of the copolymer, molecular weight samples were prepared using the following method. The resin composition was added dropwise to purified water to precipitate the copolymer, and the precipitate was collected by filtration using a Buchner funnel. The precipitate was rinsed with purified water directly over the Buchner funnel, and then dissolved in tetrahydrofuran (THF) to obtain a solution. The obtained solution was again added dropwise to purified water, and the above filtration and washing steps with purified water were repeated to redissolve the precipitate in THF, which was then used as a sample for molecular weight measurement.

[0156] (Measurement of molecular weight) Molecular weight was measured using gel permeation chromatography (GPC) equipped with an RI detector, with samples for molecular weight analysis. An HLC-8320GPC (manufactured by Tosoh Corporation) was used, with three separation columns connected in series. The packing materials were, in order, Tosoh Corporation's "TSK-GEL SUPER AW-4000," "AW-3000," and "AW-2500." The oven temperature was 40°C, and the eluent was a 30mM triethylamine and 10mM LiBr N,N-dimethylformamide solution. Measurement was performed at a flow rate of 0.6 mL / min. The sample concentration was adjusted to 1% using the above eluent solvent, and 20 microliters were injected. The average molecular weight is expressed as a polystyrene equivalent.

[0157] <Content of alkylene structural units and nitrile group-containing structural units in copolymers> (Preparation of samples for IR measurement) The resin composition was added dropwise to purified water to precipitate the copolymer, and the precipitate was collected by filtration using a Buchner funnel. The precipitate was then rinsed with purified water directly over the Buchner funnel, and dried in a hot air oven at 140°C for 1 hour to prepare a sample for IR measurement. (IR measurement) Using samples for IR measurement, the content of alkylene structural units and nitrile group-containing structural units of the copolymer in the resin composition was calculated by measuring with a Fourier transform infrared spectrometer (ThermoFisher Scientific, Nicleti S5).

[0158] <Measuring the resistivity of resin compositions> (Preparation of samples for resistivity measurement) Capacity 250cm 3 A resin composition and N-methyl-2-pyrrolidone were weighed into a plastic container to prepare 200 parts by mass of a sample for liquid resistance measurement with a non-volatile content of 8% by mass. (Measurement of resistivity) Resistivity was measured using a resistivity meter (IEST Yuanneng Technology (registered trademark), BATTERY SLURRY RESISTIVITY BSR2300) with a sample for liquid resistance measurement, and the resistivity at 25°C was calculated. The resistivity value used was the measurement result for the middle channel.

[0159] <Measurement of alkali metal content in resin compositions> The resin composition was dried using a hot air oven, and then acid-decomposed using a microwave sample preparation device (Milestone General, ETHOS1) to calculate the alkali metals (lithium, sodium, potassium) contained in the resin composition. The alkali metal content was defined as the sum of the lithium, sodium, and potassium content.

[0160] <Initial viscosity of carbon material dispersion composition> The carbon material dispersion composition was left to stand in a constant temperature bath at 25°C for at least one hour, and then immediately tested using a Type B viscometer at a rotor speed of 100 rpm. The evaluation criteria for initial viscosity were as follows: 100 mPa·s or more and less than 500 mPa·s: ◎ (Excellent), 500 mPa·s or more and less than 1000 mPa·s: ○ (Good), 1000 mPa·s or more and 2000 mPa·s or less: △ (Acceptable), and over 2000 mPa·s: × (Poor).

[0161] <Viscosity of carbon material dispersion composition over time> The carbon material dispersion composition was left to stand in a constant temperature bath at 60°C for one week. After cooling the carbon material dispersion composition to 25°C, viscosity was immediately measured using a B-type viscometer at a rotor rotation speed of 100 rpm. The evaluation criteria for viscosity over time were as follows: 500 mPa·s to 2000 mPa·s: ◎ (Excellent), over 2000 mPa·s and up to 3000 mPa·s: ○ (Good), over 3000 mPa·s and up to 6000 mPa·s: △ (Acceptable), and over 6000 mPa: × (Poor).

[0162] <60-degree specular gloss of carbon material dispersion composition> The gloss value was used to evaluate the surface smoothness of the coating film as an indicator of the degree of dispersion of the dispersed material. The carbon material dispersion composition was coated onto a PET (polyethylene terephthalate) film using a bar coater No. 7, and then dried in a 120°C hot air oven for 5 minutes. The 60-degree specular gloss was then measured on the coated surface using a gloss meter (VG7000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS Z8741. The evaluation criteria for 60-degree specular gloss were as follows: 50 degrees or more and less than 80 degrees: ◎ (Excellent), 40 degrees or more and less than 50 degrees, or 80 degrees or more and less than 90 degrees: ○ (Good), 30 degrees or more and less than 40 degrees, or 90 degrees or more: △ (Acceptable), and less than 30 degrees: × (Poor).

[0163] <Volume resistivity of electrode film> The asphalt slurry is applied using an applicator, and the basis weight per unit area of ​​the electrode is 20 mg / cm³. 2After coating the aluminum foil in the manner described, the coating film was dried in an electric oven at 120°C ± 5°C for 25 minutes. Subsequently, the surface resistivity (Ω / □) of the dried coating film was measured using a Rolester GP (MCP-T610, probe: AP2 probe (RMH333)) manufactured by Mitsubishi Chemical Analytech Co., Ltd. After measurement, the volume resistivity (Ω·cm) of the electrode film was obtained by multiplying the measured value by the thickness of the electrode composite layer formed on the aluminum foil. The thickness of the electrode composite layer was determined by subtracting the thickness of the aluminum foil from the average value of three points measured in the electrode film using a film thickness gauge (DIGIMICRO MH-15M manufactured by Nikon Corporation) to obtain the volume resistivity (Ω·cm) of the electrode film. The evaluation criteria for volume resistivity were as follows: less than 8 Ω·cm: ◎ (Excellent), 8 Ω·cm or more and less than 12 Ω·cm: ○ (Good), 12 Ω·cm or more and less than 15 Ω·cm: △ (Acceptable), 15 Ω·cm or more: × (Poor).

[0164] <Peel strength of electrode film> The asphalt slurry is applied using an applicator, and the basis weight per unit area of ​​the electrode is 20 mg / cm³. 2 After coating the aluminum foil in the manner described, the coating film was dried in an electric oven at 120°C ± 5°C for 25 minutes. Then, two 90mm x 20mm rectangles were cut with the coating direction as the long axis. For measuring the peel strength, a benchtop tensile testing machine (Strograph E3, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used, and the 180-degree peel test method was employed. Specifically, a 100mm x 30mm double-sided tape (No. 5000NS, manufactured by Nitoms Co., Ltd.) was attached to a stainless steel plate, and the prepared battery electrode composite layer was pressed against the other side of the double-sided tape. The tape was then peeled off by pulling it from bottom to top at a constant speed (50mm / min), and the average stress at this time was defined as the peel strength. The evaluation criteria for peel strength were as follows: 1.0 N / cm or more: ◎ (Excellent), 0.7 N / cm or more but less than 1.0 N / cm: ○ (Good), 0.5 N / cm or more but less than 0.7 N / cm: △ (Acceptable), less than 0.5 N / cm: × (Poor).

[0165] <Rate characteristic evaluation of lithium-ion secondary batteries> A laminated lithium-ion secondary battery was placed in a constant temperature room at 25°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). Constant current and constant voltage charging (cutoff current 1.0mA (0.02C)) was performed with a charging current of 10mA (0.2C) and a charging termination voltage of 4.2V, followed by constant current discharge at a discharge current of 10mA (0.2C) and a discharge termination voltage of 2.5V. This operation was repeated three times, and then constant current and constant voltage charging (cutoff current (1.0mA 0.02C)) was performed with a charging current of 10mA (0.2C) and a charging termination voltage of 4.2V, followed by constant current discharge at 0.2C and 3C until the discharge termination voltage reached 2.5V, and the discharge capacity was determined for each. The rate characteristic can be expressed as the ratio of the 0.2C discharge capacity to the 3C discharge capacity, as shown in Equation 2 below. (Equation 2) Rate characteristic = 3C discharge capacity / 3rd 0.2C discharge capacity × 100 (%) The rating characteristics evaluation criteria were as follows: ◎ (Excellent) for rating characteristics of 80% or higher, ○ (Good) for 70% or higher but less than 80%, △ (Acceptable) for 60% or higher but less than 70%, and × (Poor) for less than 60%.

[0166] <Evaluation of High-Temperature Cycle Characteristics of Lithium-ion Secondary Batteries> A laminated lithium-ion secondary battery was placed in a constant temperature room at 45°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). Constant current constant voltage charging (cutoff current 1.25mA (0.025C)) was performed with a charging current of 50mA (1C) and a charging termination voltage of 4.2V, followed by constant current discharge with a discharge current of 50mA (1C) and a discharge termination voltage of 2.5V. This operation was repeated 100 times. 1C was defined as the current value required to discharge the theoretical capacity of the positive electrode in one hour. The cycle characteristics can be expressed by the ratio of the 1C discharge capacity at 100 cycles to the 1C discharge capacity at 3 cycles at 45°C, as shown in Equation 3 below. (Formula 3) High-temperature cycle characteristics = 1C discharge capacity at 100 cycles / 1C discharge capacity at 3 cycles × 100 (%) The evaluation criteria for high-temperature cycle characteristics were as follows: cycle characteristics of 90% or higher were marked ◎ (Excellent), 85% or higher but less than 90% were marked ○ (Good), 80% or higher but less than 85% were marked △ (Acceptable), and less than 80% were marked × (Poor).

[0167] (Example 1-1) 780 parts by mass of NMP were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the mixture was purged with nitrogen gas. The reaction vessel was then heated to 80°C, 200 parts of HNBR1 were added, and the mixture was stirred until the hydrogenated nitrile butadiene rubber was completely dissolved. Then, 20 parts by mass of NaOH dispersion were added, and the mixture was stirred while adding air. The reaction vessel was heated while maintaining the temperature at 80°C for 12 hours to obtain copolymer (X), which is copolymer (A1), and a resin composition (R-1) containing alkali metals. Based on a total content of 100% by mass of alkylene structural units and nitrile group-containing structural units in copolymer (A1), the alkylene structural units accounted for 66% by mass, and the nitrile group-containing structural units accounted for 34% by mass. The number-average molecular weight (Mn) was 18,000, the weight-average molecular weight (Mw) was 30,000, and the Z-average molecular weight (Mz) was 49,000. Furthermore, the other structural units constituting copolymer (A1) were 3% by mass or less, based on 100% by mass of copolymer (A1). Furthermore, the alkali metal content in the resin composition was 700 ppm.

[0168] (Examples 1-2 to 1-9), (Comparative Examples 1-1 to 1-5, 1-7 to 1-9) Resin compositions (R-2 to R-9) and comparative resin compositions (RC-1 to RC-5, RC-7 to RC-9) containing the copolymer (X) etc. listed in Table 1 were obtained by the same method as in Example 1-1, except that the conditions listed in Table 1 were changed.

[0169] (Examples 1-10) The resin composition 9 prepared in Examples 1-9 was subjected to a three-pass dispersion treatment using a high-pressure homogenizer (Starburst Lab, manufactured by Sugino Machine Co., Ltd.). The dispersion treatment was carried out at a nozzle diameter of 0.17 mm and a pressure of 150 MPa to obtain a resin composition (R-10) containing copolymer (E2).

[0170] (Examples 1-11) The resin composition 9 prepared in Examples 1-9 was subjected to a five-pass dispersion treatment using a high-pressure homogenizer (Starburst Lab, manufactured by Sugino Machine Co., Ltd.). The dispersion treatment was carried out at a nozzle diameter of 0.17 mm and a pressure of 150 MPa to obtain a resin composition (R-11) containing copolymer (E3).

[0171] (Examples 1-12) HNBR1 was subjected to a five-pass dispersion treatment using a high-pressure homogenizer (Starburst Lab, manufactured by Sugino Machine Co., Ltd.). The dispersion treatment was carried out at a nozzle diameter of 0.17 mm and a pressure of 150 MPa to obtain a resin composition (R-12) containing copolymer (A4).

[0172] (Comparative Examples 1-6) Comparative resin composition 5, prepared in Comparative Examples 1-5, was subjected to a five-pass dispersion treatment using a high-pressure homogenizer (Starburst Lab, manufactured by Sugino Machine Co., Ltd.). The dispersion treatment was carried out at a nozzle diameter of 0.17 mm and a pressure of 150 MPa to obtain a resin composition (RC-6) containing copolymer (E5).

[0173] Table 2 shows the content of alkylene structural units and nitrile group-containing structural units, respectively, based on a total content of 100% by mass of alkylene structural units and nitrile group-containing structural units. In all copolymers, the other structural units constituting the copolymer were 3% by mass or less, based on 100% by mass of the copolymer.

[0174] [Table 1]

[0175] Table 2 shows the evaluation results of the resin compositions prepared in Examples 1-1 to Comparative Examples 1-9.

[0176] [Table 2]

[0177] (Example 2-1) 87.75 parts of N-methyl-2-pyrrolidone (NMP) and 8.75 parts of resin composition (R-1) were added to a stainless steel container and stirred with a disperser. Then, 3.5 parts of carbon nanotubes (JEIO, JENOTUBE6A) were weighed out and added while stirring with a disperser. A fine emulsion screen was attached to a high-shear mixer (L5M-A, SILVERSON) and batch dispersion was performed at a speed of 9000 rpm until the mixture was uniform and the dispersed particle size was 200 μm or less as measured by a grind gauge. Finally, a carbon material pre-dispersed composition was prepared by passing it through a high-magnetic-force magnetic filter (Eishin, surface magnetic flux density 17000 gauss). Subsequently, the carbon material pre-dispersion composition was supplied and subjected to a circulating dispersion treatment with a residence time of 10 minutes (bead filling rate 80%, peripheral speed 13 m / s) using a bead mill (manufactured by Ashizawa Finetech Co., Ltd., Mugen Flow®) filled with 1.0 mmφ zirconia beads. The number of cycles was 50. Next, the dispersion liquid was supplied to a high-pressure homogenizer (manufactured by Sugino Machine Co., Ltd., Starburst Lab) and subjected to a 15-pass dispersion treatment. The dispersion process was carried out using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. The dispersion liquid was then supplied to an electromagnet (manufactured by Taiho Magnetic Co., Ltd., EMF-100S, magnetic flux density 16,000 gauss, spatial volume 1.7 L, electromagnet equipped with 31 grid screens with a diameter of 10 cm and a thickness of 1.3 cm), and after three pass-through processing, the mixture was passed through two depth filters (manufactured by 3M, PP nonwoven fabric depth cartridge NT-T series, filtration accuracy 20 μm) installed in series to obtain carbon material dispersion composition 1.

[0178] (Examples 2-2 to 2-16), (Comparative Examples 2-1 to 2-9) Except for changing the dispersion conditions, carbon material, resin composition, amount of resin composition added, and NMP listed in Table 3, carbon material dispersion compositions 2 to 16 and comparative carbon material dispersion compositions 1 to 9 were obtained using the same method as in Example 2-1.

[0179] [Table 3]

[0180] Table 4 shows the evaluation results of the carbon material dispersion compositions prepared in Examples 2-1 to 2-16 and Comparative Examples 2-1 to 2-9.

[0181] [Table 4]

[0182] (Example 3-1) Capacity 150cm 3 In a plastic container, 18.8 parts by mass of an NMP solution containing 8% by mass of PVDF (polyvinylidene fluoride, Solvay, Solef #5130) and 14.5 parts by mass of NMP were weighed out. Then, 11.4 parts by mass of a carbon material dispersion composition (carbon material dispersion composition 1) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310). Subsequently, 98.1 parts by mass of a positive electrode active material (BASF Toda Battery Materials LLC, HED® NCM-111 1100) was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to obtain an asphalt slurry (asphalt slurry 1).

[0183] Next, the asphalt slurry (asphalt slurry 1) was applied using an applicator, with a basis weight of 20 mg / cm³ per unit area of ​​the electrode. 2 After coating the aluminum foil in this manner, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain the electrode film (electrode film 1). Subsequently, the electrode film (electrode film 1) was rolled using a roll press (Sankmetal, 3t hydraulic roll press) to obtain the positive electrode (positive electrode 1). The basis weight per unit area of ​​the composite layer was 20 mg / cm². 2 The density of the asphalt layer after rolling was set to 3.1 g / cc.

[0184] (Examples 3-2 to 3-5, Examples 3-8 to 3-16), (Comparative Examples 3-1 to 3-9) As shown in Table 5, composite slurries 2-5, 8-16, comparative composite slurries 1-9, electrode films 2-5, 8-16, comparative electrode films 1-9, positive electrodes 2-16, and comparative positive electrodes 1-9 were obtained by the same method as in Example 3-1, except that carbon material dispersion compositions 2-16 and comparative carbon material dispersion compositions 1-9 were used instead of carbon material dispersion composition 1.

[0185] (Examples 3-6) Capacity 150cm 3 In a plastic container, 18.8 parts by mass of an NMP solution containing 8% by mass of PVDF (polyvinylidene fluoride, Solvay, Solef #5130) and 18.9 parts by mass of NMP were weighed out. Then, 7.1 parts by mass of a carbon material dispersion composition (carbon material dispersion composition 1) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310). Subsequently, 98.1 parts by mass of a positive electrode active material (BASF Toda Battery Materials LLC, HED® NCM-111 1100) was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to obtain an asphalt slurry (asphalt slurry 6).

[0186] Next, the asphalt slurry (asphalt slurry 6) is applied using an applicator, with a basis weight of 20 mg / cm³ per unit area of ​​the electrode. 2 After coating the aluminum foil in this manner, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain the electrode film (electrode film 6). Subsequently, the electrode film (electrode film 1) was rolled using a roll press (Sankmetal, 3t hydraulic roll press) to obtain the positive electrode (positive electrode 6). The basis weight per unit area of ​​the composite layer was 20 mg / cm². 2 The density of the asphalt layer after rolling was set to 3.1 g / cc.

[0187] (Examples 3-7) Capacity 150cm 3In a plastic container, 18.8 parts by mass of an NMP solution containing 8% by mass of PVDF (polyvinylidene fluoride, Solvay, Solef #5130) was weighed, along with 21.6 parts by mass of NMP. Then, 5.0 parts by mass of a carbon material dispersion composition (carbon material dispersion composition 1) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Awatori Rentaro, ARE-310). Subsequently, 97.5 parts by mass of a positive electrode active material (BASF Toda Battery Materials LLC, HED® NCM-111 1100) was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a rotation / revolution mixer (Awatori Rentaro, ARE-310) to obtain an asphalt slurry (asphalt slurry 7).

[0188] Next, the asphalt slurry (asphalt slurry 7) was applied using an applicator, with a basis weight of 20 mg / cm³ per unit area of ​​the electrode. 2 After coating the aluminum foil in this manner, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain the electrode film (electrode film 7). Subsequently, the electrode film (electrode film 1) was rolled using a roll press (Sankmetal, 3t hydraulic roll press) to obtain the positive electrode (positive electrode 6). The basis weight per unit area of ​​the composite layer was 20 mg / cm². 2 The density of the asphalt layer after rolling was set to 3.1 g / cc.

[0189] Table 5 shows the evaluation results of the electrode films prepared in Examples 3-1 to 3-16 and Comparative Examples 3-1 to 3-9.

[0190] [Table 5]

[0191] (Example 4-1) The positive electrode (positive electrode 1) and the standard negative electrode were punched out to 45mm x 40mm and 50mm x 45mm respectively, and a separator (porous polypropylene film) to be inserted between them was placed in an aluminum laminate bag and dried in an electric oven at 60°C for 1 hour. Then, in a glove box filled with argon gas, 2 mL of electrolyte (a non-aqueous electrolyte prepared by mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a 1:1:1 (volume ratio) mixture, and further adding 2 parts by mass of VC (vinylene carbonate) as an additive per 100 parts by mass of the mixed solvent, and then dissolving LiPF6 at a concentration of 1M) was injected, and the aluminum laminate bag was sealed to produce a laminate-type lithium-ion secondary battery (secondary battery 1).

[0192] (Examples 4-2 to 4-16), (Comparative Examples 4-1 to 4-9) Laminated lithium-ion secondary batteries (secondary batteries 2) to (comparative secondary batteries 9) were manufactured using the same method as the laminated lithium-ion secondary battery (secondary battery 1), except that the positive electrode was changed as shown in Table 6.

[0193] [Table 6]

[0194] In the above example, a resin composition containing copolymer (X) and an alkali metal in an amount of 50 ppm to less than 10,000 ppm was used, wherein the resistivity of the resin composition when the copolymer content was reduced to 8% by mass using N-methyl-2-pyrrolidone was 5,000 Ω·cm to 25,000 Ω·cm. In the example, compared to the comparative example, the viscosity stability of the carbon material dispersion composition over time was excellent, and a lithium-ion secondary battery with excellent secondary battery characteristics, particularly high-temperature cycle characteristics, was obtained. Therefore, it has become clear that this disclosure can provide a lithium-ion secondary battery with high capacity, high output, and high durability that is difficult to achieve with conventional carbon material dispersion compositions. Vehicles equipped with the lithium-ion secondary battery of this disclosure have high charge and discharge performance and excellent high-temperature cycle characteristics, resulting in vehicles that are highly safe and have improved fuel efficiency.

[0195] Although the present invention has been described above with reference to embodiments, the present invention is not limited thereto. Various modifications to the structure and details of the present invention can be made that are understandable to those skilled in the art within the scope of the invention.

Claims

1. A polymer (X) having alkylene structural units and nitrile group-containing structural units, and a resin composition containing an alkali metal, The alkali metal content is 50 ppm or more and less than 10,000 ppm. A resin composition having a resistivity of 5,000 Ω·cm or more and 25,000 Ω·cm or less when the non-volatile content of the resin composition is reduced to 8% by mass with N-methyl-2-pyrrolidone.

2. The resin composition according to claim 1, wherein the Z-average molecular weight of the copolymer (X) is 20,000 or more and 200,000 or less.

3. The resin composition according to claim 1, wherein the ratio (Mz / Mw) of the Z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the copolymer (X) is 2.0 or less.

4. A carbon material dispersion composition comprising a resin composition according to any one of claims 1 to 3 and a carbon material.

5. A composite slurry comprising the carbon material dispersion composition according to claim 4 and an active material.

6. An electrode film coated with the composite slurry described in claim 5.

7. A secondary battery comprising an electrode having the electrode film described in claim 6 and an electrolyte.

8. A vehicle equipped with the secondary battery described in claim 7.

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